The present invention relates to a cleaning apparatus having a cleaning member which is adapted to be brought into contact with a surface of a workpiece to be cleaned, such as a semiconductor wafer, and effect cleaning of the surface of the workpiece.
A workpiece such as a semiconductor wafer which has been subjected to polishing or chemical treatment in a polishing apparatus has a contaminated surface. In order to clean the surface of the workpiece, a scrubbing apparatus has been conventionally used.
The phase scrubbing apparatus herein means a cleaning apparatus in which a cleaning member, such as a sponge, is rotated and pressed against a workpiece to be cleaned, which is also rotated, to thereby scrub the surface of the workpiece. As the cleaning member, a column type cleaning member or a pencil type cleaning member is used.
In a conventional scrubbing apparatus, in order to ensure that the cleaning member applies a predetermined pressure to the workpiece to be cleaned, a member attached to the cleaning member, such as an arm, is controlled to be positioned at a predetermined distance from the workpiece when the cleaning member is pressed against the workpiece.
However, when the pressure applied to the workpiece by the cleaning member, such as a sponge, is controlled in such a manner as mentioned above, it is difficult to maintain the pressure exerted by the sponge at a predetermined level. That is, a problem occurs, such that when the cleaning member, such as a sponge, undergoes permanent deformation or wear as a result of prolonged use, the pressure exerted by the sponge changes from that exerted in an early period.
As a countermeasure for the above-mentioned problem, it has been considered to employ a method in which the pressure exerted by the cleaning member is controlled by connecting a load measuring device to the member attached to the cleaning member and monitoring an output of the load measuring device so as to maintain the output of the load measuring device at a predetermined level.
However, the above-mentioned method requires a complicated structure. In addition, it is difficult to adjust the pressure exerted by the cleaning member following a slight change in load applied to the workpiece.
On the other hand, there is a mechanism in which the pressure exerted by the cleaning member is controlled by providing a spring, an air cylinder or a balancing weight between the cleaning member and a drive motor for rotating the cleaning member, or between the cleaning member and drive motor as a whole and a vertical drive mechanism for vertically moving the cleaning member and drive motor.
However, the above-mentioned mechanism simply utilizing a spring, an air cylinder or a balancing weight results in the occurrence of an undesirable shift of movable members associated with the cleaning member with a consequent high friction between the movable members and stationary members. Therefore, this mechanism is unsuitable for maintaining a load applied to a workpiece at a predetermined level by smooth adjustment following a slight change in the load.